R4,800 bill on my data account

I had an account with Nashua Mobile which was a 20Gig cell c deal. I was paying R189 per month for 5gig day time data and 15gig night time data. My contract got transferred to Autopage and now I have just been charged R4,848.34 for data usage for November 2015. I wrote to Autopage service department on 4 occasions and I was told that the matter was closed from 10th through to 17th November,2015 and the service department advised me that the matter was closed. They still decided to deduct the funds from my account and they say that I used the data. My money has literary been ****** out of my account by this company and they think they will get away with it...